The major purpose of this investigation is to explore control of SV40 gene expression both in lytically-infected cells and in virus-transformed cells. Current knowledge of the SV40 genetic map allows the assignment of certain genomic regions to control elements for gene expression. These include the origin of replication, promoters and terminators for RNA synthesis, sites for RNA processing and transport, sites involved in post-transcriptional modification of RNA (capping, polyadenylation, etc.), sites involved in early gene autoregulation, and ribosome binding-protein synthesis initiation sites. Deletion mutants will be constructed in regions of the genome related to these functions. Biochemical methods will be developed to allow preparation of a diverse set of deletion and point mutants in these regions. The molecular biology of these mutants will be studied in attempts to understand how SV40 gene expression is controlled. Cells transformed by appropriate mutants will be studied in attempts to understand the interaction of viral and cellular genetic elements leading to cellular transformation and oncogenesis.